Follow these detailed steps carefully to build layers of flavor, ensuring your mushrooms are perfectly browned and your rice is fluffy and infused with taste. The key is patience, especially when allowing the mushrooms to caramelize and the rice to toast.

1. Prepare the Mushrooms: Begin by heating the olive oil and one tablespoon of the butter in a large skillet or Dutch oven over medium-high heat. Once the butter is melted and foaming, add the sliced cremini mushrooms in a single layer. It’s crucial not to overcrowd the pan; if necessary, cook the mushrooms in two batches. Let them cook, undisturbed, for 3-4 minutes until the bottom side is golden brown. Stir and continue to cook for another 4-5 minutes, allowing them to release their moisture and develop a deep, caramelized color. This browning process is essential for developing a rich, meaty flavor. Once browned, season them with a pinch of salt and pepper, then remove them from the skillet and set them aside on a plate.
2. Sauté the Aromatics: Reduce the heat to medium. Add the remaining tablespoon of butter to the same skillet. Once it’s melted, add the finely chopped yellow onion. Sauté for 5-7 minutes, stirring occasionally, until the onion becomes soft, translucent, and slightly sweet. Scrape up any browned bits left from the mushrooms on the bottom of the pan—this is pure flavor.
3. Bloom the Garlic and Toast the Rice: Add the minced garlic and dried thyme to the skillet with the onions. Cook for about 60 seconds, stirring constantly until the garlic is fragrant. Be careful not to let the garlic burn, as it will become bitter. Immediately add the uncooked long-grain rice to the skillet. Stir continuously to coat the rice grains in the butter and onion mixture. Continue toasting the rice for 2-3 minutes, until the edges of the grains look translucent and you can smell a nutty aroma. This step helps the rice grains stay separate and fluffy.
4. Deglaze and Simmer: Pour in about a half-cup of the broth to deglaze the pan. Use your wooden spoon or spatula to scrape all the remaining flavorful browned bits from the bottom of the skillet, incorporating them into the liquid. This adds immense depth to the final dish.
5. Cook the Rice: Once the pan is deglazed, pour in the remaining 3 ½ cups of broth. Stir everything together and bring the liquid to a strong simmer. Once simmering, reduce the heat to low, cover the skillet tightly with a lid, and let it cook for 15-18 minutes, or until the rice has absorbed most of the liquid. Avoid lifting the lid during this time, as it will release steam and can result in unevenly cooked rice.
6. Combine and Rest: Turn off the heat. Remove the lid and gently add the cooked mushrooms back into the skillet. Add half of the grated Parmesan cheese and half of the fresh parsley. Gently fluff the rice with a fork, mixing the mushrooms, cheese, and parsley throughout.
7. Final Rest and Serve: Place the lid back on the skillet and let the dish rest off the heat for 10 minutes. This crucial resting period allows the rice to steam fully, making it perfectly tender and fluffy. After resting, give it one final fluff with a fork. Taste and adjust seasoning with more salt and pepper if needed. Serve immediately, garnished with the remaining Parmesan cheese and fresh parsley.